The objective of the proposed studies is to determine the net effect of tricyclic drugs, desipramine and iprindole, on the locus coeruleus-hippocampal system in the rat brain. The net effect of these drugs will be inferred by examining possible changes in baseline electrical activities and receptor sensitivity of both pre- and postsynaptic neurons in this system. The tricyclic drugs will be administered both acutely and chronically so that the information obtained can be related to the delayed therapeutic effects seen in patients with depressive disorders.